What's the noun for feldspathoid? Here's the word you're looking for.
feldspar
(mineralogy) Any of a large group of rock-forming minerals that, together, make up about 60% of the earth's outer crust. The feldspars are all aluminumsilicates of the alkali metals sodium, potassium, calcium and barium. Feldspars are the principal constituents of igneous and plutonic rocks.
“When the sandstone contains appreciable quantities of feldspar the rock is called arkose.”
“A plagioclase feldspar, albite probably, occurs as parallel growths of transparent colorless to yellowish crystals.”
“These granite dikes are composed almost totally of potassium feldspar and quartz.”
feldspathoid
(mineralogy) Any of a small group of igneous, plutonic, and volcanicminerals formed in magma that did not contain enough silica to satisfy all the chemical bonds. Feldspathoids are silica-poor variants of the feldspar group.
